Batch adsorber rate analysis of Methylene Blue on Amberlite and clinoptilolite

Adsorption of Methylene Blue on clinoptilolite and on Amberlite XAD-4 was investigated in a temperature range of 20-50 degrees C, in a batch adsorber. Results of this work showed that clinoptilolite was a better sorbent than Amberlite XAD-4 for the removal of Methylene Blue. Among the four adsorption rate models tested in the analysis of the adsorption rate data, a simple single parameter diffusion model (Model C) was shown as the best model to be used in practical applications. The diffusivity found from this model was not dependent on the adsorbate concentration. Although the pseudo-first order adsorption rate model also gave good agreement with the experimental data obtained at the initial periods of the adsorption experiments, the concentration dependence of the rate constant of this model was found as the major disadvantage of this model. Results indicated that dissociative chemisorption and blocking of some of the pores during adsorption caused high tortuosity factors and a decrease in the adsorption rate. Adsorption capacity of these adsorbents were also found to be increased significantly by a decrease of the pH of the solution from 10 to 3.